Load going to Fast?

[Londerko]

[CaptnC]

It seems to me ejector marks seem to be common. I've seen a bunch of factory ammo that leaves a lot of marks. So I'm not convicted that it is a good signs of high pressure...

I'm was running 28gr of 8208 in some new 120gr bullets I just got. I'm about 80 fps behind what you are seeing.

[1Shot]

Your 28.2 grs 8208 with 123s is running right with my 28.5 grs. with 120 Sierra Pro Hunter from 18" Oden barrel. In my experience Hornady cases are soft and even factory 123 SST left slight ejector swipes in both of my rifles. But after first shot until I got over listed loads from Grendel manual I did not see swipes again. Bullets do make a difference even if same weight. 28 gr 8208 is about max with 120 Speer Gold Dots in my rifles. These load do shoot though. Hornady case, CCi 450 primers is what I am using.

[Popeye212]

On that load I backed off to 28.0 8208xbr I have the same barrel it chronos with a couple of 123's at 2524 with low SD I got the same swipes you did towards 28.5 they are just fast barrels. I am consistently getter higher velocities than others with the loads I am seeing. Just my .02 Sorry about answering the Pm's been busy. With a Creedmoor.

[Londerko]

[LR1955]

Thanks for the replys.
I was kind of suprised that the hornady Black was only 2404fps, then I was shocked when the 8208 clocked in 150fps faster with the same bullet.
The SD is way low, accuracy is good.
Now I’m curious if the marks are because of load or the soft brass.
The hornady Black leaves slight marks, but the marks on the 28.2 load are more significant .
No worries Popeye, been busy too

LD:

28 grains of 8208 with a 120 grain bullet is the max I would go. You are over it with a 123.

Might as well buy some new bolts. I figure within three or four hundred rounds or so of that load you ought to shear a lug or two.

I know, I know........ Ten different people will pop up saying they use that load and haven't sheared a lug. My response is 'yet'.

LR55

[bj139]

It is curious how bolt guns operating at far higher pressure don't show ejector marks.
It must have someting to do with ejection under pressure in a semi-auto.

[Klem]

Londerko,

Quickload predicts a peak pressure of 60,600psi for your loads (the SAAMI limit is 52,000). It also predicts 2,525fps which is pretty close to your recorded MV. It's a hot load and eventually something will break.

For that bullet weight 8208 is not the most efficient powder choice. Something slower like H4895 will get more MV for the same peak pressure.

I also wouldn't put too much stock in a standard deviation of only three numbers.

[Londerko]

[ike838]

My first thought is that you are over gassed . Adjustable gas block?

[Klem]

Leo,

28.5/8208 behind a 123AMax is even worse at 62,000lbs. I've said it before that on average the loads on this forum are hot. I'm not saying don't copy them but be prepared to hammer your gun. Breaking bolt lugs on AR's is not uncommon (probably more common than reported) given the loads guys want to run and relative to bolt guns it's a fragile action. This, and with everyone wanting to squeeze as much out of a small case as possible. Heck, I do too.

I wouldn't put too much stock in only one source of information however; be it Quickload, or this forum, or the books, or a bullet or powder manufacturer's load data. A combination of sources will give you a better idea and then do your own work-up.

For example, Nosler's online load data lists a wide variation in Grendel case volumes. Their 120gn page lists Grendel cases holding 29gn of water, compared to their 100gn page that displays 33gns of water. When I plug in their recommended loads including the 29gn of water into QL it predicts 122,500lbs. At that pressure the gun will blow. When I plug in their load but use my own measured case volume it drops down to a more reasonable 58,000lbs. Clearly they made a mistake when weighing case volumes yet it all looks respectable and convincing on a fancy manufacturers website. I've weighed Lapua cases at 35.5gns of water and Quickload's default is 36gns. CIP's default is 37gn of water. All these differences across data sources make for clumsy loading if you just follow one.

https://load-data.nosler.com/load-data/65-grendel/

According to QL, with the 123ELD the most you should load into a Lapua case at 2.283"COAL is 26.5gn of 8208. It will get you 2,370fps. Using H4895 the max load is 27gns and this will get you 2,400fps from an 18" barrel. Bearing in mind QL is notoriously conservative then another 0.1grain or two might be on the cards but bear in mind for every 0.1gn of 8208 will be roughly 500lbs pressure. Only in long range shooting will you notice a difference between a hot and mild load. In short-medium range match and hunting it's not going to make an ounce of difference, except to your gun and face.

[Londerko]

[Klem]

No argument there... Hogdgon copies ADI's data for the powder it buys from them. Bottom of page;

http://www.adi-powders.com.au/rifle/6-5mm-grendel

The differences are disconcerting for sure, but for pressures I'd give a powder manufacturer more credibility than a bullet manufacturer or QL. After all, it's what they do for a living, create the fuel that makes pressure. You'd think they know how to measure it.

[Londerko]

My first thought is that you are over gassed . Adjustable gas block?

[LtDan]

It is curious how bolt guns operating at far higher pressure don't show ejector marks.
It must have someting to do with ejection under pressure in a semi-auto.

It has a lot to do with dwell of the bolt unlocking too soon I believe